The dramatic increases in lifespan that occurred during the 20th century were due, in large part, to improvements in treatment and prevention of infectious diseases. Treatment encompasses the administration of pharmaceutical agents to patients infected with pathogenic bacteria, viruses, fungi, or protozoa. Prevention encompasses the deployment of a wide variety of techniques aimed at eliminating or reducing the number of pathogenic bacteria, viruses, fungi, or protozoa in the environment outside the body as well as prophylactic therapy. With the ever-increasing number of disinfecting agents and pharmaceutical compounds has come an increased need for methods of selecting an appropriate compound or combination thereof to combat a particular pathogen.
Frequently selection of an appropriate pharmaceutical agent or agents involves determining the response of a biological sample to the compound. For example, before prescribing an antibiotic for an infection it is desirable to know whether the infectious agent, e.g., a bacterium, fungus, virus, protozoan, etc., is sensitive to the antibiotic. Thus if the infectious agent is a bacterium, it may be desirable to know whether the antibiotic exerts a bacteriostatic or bacteriocidal effect on the bacterium. Predictions of sensitivity may be made based on the identity of the bacterium. However, the increasing prevalence of drug-resistant bacteria has made it increasingly important to assess sensitivity by directly contacting the bacterium with a candidate antibiotic. Similar considerations hold in the case of selecting an appropriate disinfecting agent.
Antibiotic sensitivity testing typically involves obtaining a biological sample presumed to contain the infectious agent. The sample, or a suspected pathogen or pathogens obtained from the sample, is then contacted with various compounds, and the response of the suspected pathogen is assessed. For example, the ability of a bacterium to multiply in the presence of the compound may be compared with the ability of the bacterium to multiply in the absence of the compound. Various techniques may be used to contact the suspected pathogen with candidate compounds. Traditionally, antibiotic susceptibility testing has often involved culturing infectious agents in relatively large vessels, receptacles, or trays into which appropriate culture medium, candidate compounds, and biological samples are placed. However, current test systems suffer from a number of drawbacks that limit their usefulness and flexibility for these and other applications. The present invention addresses some of these limitations.